Hydroxyphenyl phosphine oxide mixtures and their use as flame retardants for epoxy resins

ABSTRACT

A hydroxyphenyl or alkoxyphenyl phosphine oxide composition comprising (i) a first mixture of mono-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers, (ii) a second mixture of bis-(hydroxyaryl) or (alkoxyphenyl) phosphine oxide isomers, (iii) a third mixture of tris-(hydroxyaryl) or (alkoxyphenyl) phosphine oxide isomers, and optionally iv) a minority amount of non-hydroxy or non-alkoxy tris-phenyl phosphine oxides is provided. Also provided are epoxy resins compositions with excellent flame retardancy and physical properties, which resins comprise the phosphine oxide composition.

This application a divisional of U.S. patent application Ser. No.12/807,642, filed Sep. 10, 2010, now U.S. Pat. No. 8,404,861, whichclaims benefit under 35 USC 119(e) of U.S. provisional application No.61/241,562, filed Sep. 11, 2009, the disclosures of which isincorporated by reference.

FIELD

This invention relates to certain hydroxyphenyl and alkoxyphenylphosphine oxide mixtures and their use as flame retardants for epoxyresins.

BACKGROUND

Composite materials based on epoxy resins are used in a variety ofapplications and continue to have considerable importance because oftheir versatility. A specific example of such an application is in theproduction of electrical laminates used in printed circuit boards(printed wiring boards, PWB). A key requirement of this and many otherapplications is flame resistance. Accordingly, it has been customary inthe preparation of epoxy-containing laminates to incorporate variousadditives to improve the flame retardancy of the resulting laminate.Many types of flame retardant substances have been used, however, themost common thus far used commercially have been halogen containingcompounds, such as tetrabromobisphenol A. Typically, in order to reachthe desired fire retardancy level (V-0 in the standard “UnderwritersLaboratory” test method UL 94), levels of such bromine-containing flameretardant substances are required that provide a bromine content from 10weight percent to 25 weight percent based on the total weight in theproduct.

Generally, halogen-containing fire retardant epoxy resins, such as thosecontaining tetrabromobisphenol A, are considered to be safe andeffective. However, there has been increasing interest in the industryto utilize flame-retarded epoxy systems that are not based on halogenchemistry. However, these replacement materials must still be able tomeet the requirements of fire retardancy and to display the sameadvantages of mechanical properties, toughness, and solvent and moistureresistance that are offered by the halogenated materials currently used.

One alternative approach has been the use of phosphorus based fireretardants. See for example, EP 0 384 939 and U.S. Pat. Nos. 5,817,736;5,759,690; 5,756,638, 5,648,171; 5,587,243; 5,576,357; 5,458,978;5,376,453; and 5,036,135; all of which are incorporated herein byreference in their entirety. In all of these references, a formulationis formed from the reaction of a flame retardant derived from aphosphorus compound and an epoxy resin, which is then cured with anamino cross-linker such as dicyandiamide, sulfanilamide, or some othernitrogen element containing cross-linker to form the thermosettingpolymer network.

Specific examples of commercially available phosphorus-based fireretardant additives include Antiblaze® 1045 (Albright and Wilson Ltd,United Kingdom) which is a phosphonic acid ester. Phosphoric acid estershave also been used as additives, such as, for example, PX-200(Diahachi, Japan). Other commercially available reactive phosphoruscontaining compounds disclosed as being suitable for epoxy resinsinclude Sanko HCA and Sanko HCA-HQ (Sanko Chemical Co., Ltd., Japan).

Alkyl and aryl substituted phosphonic acid esters are particularlycompatible with epoxy resins. However, these phosphonic acid esters areoften unsatisfactory as substitutes for halogenated flame retardants inepoxy resins for the production of electrical laminates. For example,these materials are known to be plasticizers and thus laminates formedtherefrom tend to exhibit undesirably low glass transition temperatures(Tg). An additional drawback is that the use of phosphonic acid estersin amounts sufficient to provide the necessary flame retardancyincreases the tendency of the resulting cured epoxy resin to absorbmoisture. The moisture absorbency of cured laminate board is verysignificant, because laminates containing high levels of moisture tendto blister and fail, when subjected to the soldering operationstypically employed in the manufacture of printed wiring boards.

Various other phosphorus based flame retardant materials are describedin the literature, which are either too expensive or feature certaininferior properties. For example, EP 0 754 728 discloses a cyclicphosphonate as a flame retardant material, which is incorporated into anepoxy resin. However, the cyclic phosphonate must be present in largequantities, such as in excess of 18 weight percent, in order for theresin system to meet UL 94 V-0 rating. This loading for the phosphonatecompound may lead to a depression of the Tg or higher moistureabsorption. EP 1 116 774 utilizes a hydrogen phosphinate,9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, in conjunction withtriphenylphosphine oxide. However, the epoxy resin base requires the useof non-standard epoxy resins; namely a xylene-modified novolak resin andnaphthylene aralkyl and biphenyl-modified epoxy resins.

Various other phosphorus compounds have also been used to preparehalogen-free flame retardant epoxy resins useful in the manufacture ofcomposite materials. For example, the use of phosphorus-carbon bondedmoieties, such as phosphine oxides, have been disclosed in WO 01/42253;U.S. Pat. No. 4,345,059; EP 1 116 774; JP2000186186 and JP 05057991B4;all of which are incorporated herein by reference in their entirety.Such phosphine oxides display benefits of improved resistance tomoisture uptake when compared with other phosphorus compounds thatcontain P—O bonded moieties, as disclosed in WO 01/42253. However, a keydisadvantage of these compositions is that they are costly to prepare,because they utilize unique raw materials. For example, JP2000186186discloses the use of pure bis(p-hydroxyphenyl)phenyl-phosphine oxide,which requires the use of a pure dichlorophenyl phosphine in itsproduction. Similarly, JP 05057991B4 discloses the production oftris-(m-gylcidyloxyphenyl)phosphine oxide by reacting the pure metaphenol with epichlorohydrin. In an analogous manner, the phosphineoxides utilized in WO 01/42253 require lithium reagents and cryogenicreaction conditions, thus requiring special equipment for itsmanufacture.

In U.S. Pat. No. 6,733,698 there is disclosed a mixture ofhydroxyarylphosphine oxides comprising (a) a mono(hydroxyaryl)phosphineoxide, (b) a bis(hydroxyaryl)phosphine oxide, (c) atris(hydroxyaryl)phosphine oxide, and, optionally (d) a tri-aryl, alkylor aralkyl-substituted phosphine oxide. The mixture is produced byreacting a mixed Grignard reagent with phosphorus oxychloride and issaid to be useful in the preparation of polyglycidyl ethers and as aflame retardant in epoxy resin compositions which can be processed intoresin-impregnated composites.

U.S. Pat. No. 6,740,732 discloses phosphorus element-containingcrosslinking agents for epoxy resin compositions based on isomericmixtures of tris(2-hydroxyphenyl)phosphine oxides having the followinggeneral chemical structure:

wherein R may be independently a hydrogen or a C₁-C₁₀ alkyl group.

The present invention provides a novel composition comprising mixturesof ortho and para isomers of mono-, bis- and tris-(hydroxyphenyl)phosphine oxide compounds which is useful as a flame retardant in epoxyresin formulations. The composition is readily prepared from reactionmixtures of ortho and para halogenated phenolic ethers, e.g., a mixtureof 2- and 4-bromoanisole, which mixture is conveniently andinexpensively obtained using a two step process whereby a phenolate saltis treated with an alkyl halide to produce phenol ether/halide saltmixture followed by oxidation e.g., by addition of peroxide. The presentcomposition is therefore significantly less expensive to produce thanmany of the phosphorous containing flame retardants suggested in theprior art, such as U.S. Pat. No. 6,733,698, yet endows polymercompositions with equal or better flame retardant and physicalproperties when the appropriate ortho to para ratios are selected.

It is possible to prepare compositions similar to those of the presentinvention comprising only the tris-(hydroxyphenyl) phosphine oxides ofthe present invention without the mono- and bis-(hydroxyphenyl)phosphine oxides found herein, however such mixtures do not alwaysprovide the full compliment of exceptional properties obtained whenusing the present compositions.

SUMMARY

In one aspect, the invention resides in a hydroxyphenyl or alkoxyphenylphosphine oxide composition comprising:

(i) a first mixture of mono-(hydroxyphenyl) or (alkoxyphenyl) phosphineoxide isomers each having the formula (I):

(ii) a second mixture of bis-(hydroxyphenyl) or (alkoxyphenyl) phosphineoxide isomers each having the formula (II):

(iii) a third mixture of tris-(hydroxyphenyl) or (alkoxyphenyl)phosphine oxide isomers each having the formula (III):

wherein R is hydrogen or an alkyl group containing from 1 to 6 carbonatoms, R¹ and R² are the same or different and each is an alkyl groupcontaining from 1 to 6 carbon atoms, each of x and y is an integer from0 through 4, and each OR group is in the ortho or para position withrespect to the bond between the P atom and the associated phenyl groupsuch that, for each mixture (i), (ii) and (iii), the ratio of the numberof OR groups in the ortho-position with respect to the bond between theP atom and the associated phenyl group to the number of OR groups in thepara-position with respect to the bond between the P atom and theassociated phenyl group is from about 20:80 to about 1:99, for examplefrom about 10:90 to about 2:98, such as from about 6:94 to about 3:97.Typically the composition will also contain a certain amount ofnon-alkoxy or non-hydroxy tris-phenyl phosphine oxide as well.

Conveniently, each of x and y is zero and R is hydrogen.

Conveniently, said composition comprises about 10 to about 50 wt % ofthe first mixture (i), about 30 to about 60 wt % of the second mixture(ii) and about 10 to about 50 wt % of the third mixture (iii).

In a further aspect, the invention resides in a method of producing thealkoxyphenyl phosphine oxide composition described herein, the methodcomprising:

(a) reacting phenol with an alkyl halide having 1 to 6 carbon atoms inthe presence of an alkali metal base to produce a first product mixturecomprising an alkoxybenzene and an alkali metal halide;

(b) contacting said first product mixture with an oxidizing agent underconditions such that the alkali metal halide reacts with thealkoxybenzene to produce a first mixture of ortho andpara-haloalkoxybenzenes;

(c) reacting said first reaction mixture with magnesium;

(d) adding a benzene halide to the mixture produced in (c) and reactingthe benzene halide with magnesium to produce a mixture of alkoxy andnon-alkoxy benzene Grignard reagents; and

(e) reacting said mixture of alkoxy and non-alkoxy benzene Grignardreagents with phosphorus oxychloride to produce said composition whereinR in each of formulas (I), (II) and (III) is an alkyl group containingfrom 1 to 6 carbon atoms.

Conveniently, the alkyl halide comprises methyl bromide and theoxidizing agent comprises hydrogen peroxide.

In one embodiment, the method further comprises reacting the product of(e) with an acid to produce the corresponding hydroxyphenyl phosphineoxide composition wherein R in each of formulas (I), (II) and (III) ishydrogen.

In yet a further aspect, the invention resides in an epoxy resincomposition comprising the reaction product of the hydroxyphenylphosphine oxide composition described herein, wherein R in each offormulas (I), (II) and (III) is hydrogen, and an epihalohydrin.

In still yet a further aspect, the invention resides in a curable epoxyresin composition comprising (a) an epoxy resin and (b) a cross-linkingsystem comprising the hydroxyphenyl phosphine oxide compositiondescribed herein, wherein R in each of formulas (I), (II) and (III) ishydrogen.

DETAILED DESCRIPTION

The hydroxyphenyl or alkoxyphenyl phosphine oxide composition of theinvention comprises:

(i) a first mixture of mono-(hydroxyphenyl) or (alkoxyphenyl) phosphineoxide isomers each having the formula (I):

(ii) a second mixture of bis-(hydroxyaryl) or (alkoxyphenyl) phosphineoxide isomers each having the formula (II):

(iii) a third mixture of tris-(hydroxyaryl) or (alkoxyphenyl) phosphineoxide isomers each having the formula (III):

wherein R is hydrogen or an alkyl group containing from 1 to 6 carbonatoms, R¹ and R² are the same or different and each is an alkyl groupcontaining from 1 to 6 carbon atoms, each of x and y is an integer 0, 1,2, 3 or 4, and each OR group is in the ortho or para position withrespect to the bond between the P atom and the associated phenyl groupsuch that, for each mixture (i), (ii) and (iii), the ratio of the numberof OR groups in the ortho-position with respect to the bond between theP atom and the associated phenyl group to the number of OR groups in thepara-position with respect to the bond between the P atom and theassociated phenyl group is from about 20:80 to about 1:99, for example,from about 10:90 to about 2:98, such as from about 6:94 to about 3:97.

Generally, R in each of formulas (I), (II) and (III) is hydrogen or analkyl group containing from 1 to 3 carbon atoms, especially hydrogen ora methyl group. As will become apparent from the ensuing discussion, inits as-synthesized form, the present composition will generally compriseisomers of formulas (I), (II) and (III) in which R is an alkyl group.However, before use of the composition in the production of an epoxyresin, the composition is generally converted to an active form, inwhich some or all of the R groups are hydrogen. Such conversion isreadily achieved by treating the composition with an acid, such ashydrogen bromide.

Generally, each of R¹ and R² in formulas (I), (II) and (III) is an alkylgroup containing from 1 to 3 carbon atoms, especially a methyl group.However, each of x and y in formulas (I), (II) and (III) is generallyeither zero or 1, especially zero.

Conveniently, the present composition comprises from about 10 to about50, such as from about 15 to about 30, wt % of the first mixture (i),from about 30 to about 60, such as from about 40 to about 55, wt % ofthe second mixture (ii) and from about 10 to about 50, such as fromabout 15 to about 30, wt % of the third mixture (iii).

In addition, as discussed in greater detail below, the composition willalso normally contain triphenyl phosphine oxide compounds of the formulaIV:

in amounts up to 10 wt %, i.e., from 0 to 10 wt % of the product.

The present composition can readily be produced by a process in whichphenol is initially reacted with an alkyl halide having 1 to 6 carbonatoms, generally methyl bromide, in the presence of an alkali metalbase, such as sodium or potassium hydroxide, to produce a first productmixture comprising an alkoxybenzene and an alkali metal halide. Thereaction is typically conducted at a temperature of about 50° C. toabout 90° C. for about 1 to about 3 hours and can be represented asfollows:

The first product mixture is then contacted with an oxidizing agent,such as hydrogen peroxide, under conditions such that the alkali metalhalide reacts with the alkoxybenzene to produce a mixture of ortho andpara-haloalkoxybenzenes. The oxidation reaction is typically conductedat a temperature of about 20° C. to about 40° C. for about 1 to about 4hours and can be represented as follows:

The resulting mixture of ortho and para-haloalkoxybenzenes, is isolatedby phase separation and, optionally, distillation, without separation ofthe individual isomers, and then dried to remove trace moisture. For thecase of ortho- and para-bromoanisole, the isomers have the same boilingpoints. The dried mixture of ortho and para-haloalkoxybenzenes is thenis then reacted with magnesium to produce a mixture of Grignardreagents, to which is added an unsubstituted or alkyl-substitutedhalobenzene, such as benzene chloride. The resultant mixture is furtherreacted with magnesium to convert the halobenzene to an additionalGrignard reagent. Phosphorus oxychloride is then added to this mixtureto produce the required composition wherein R in formulas (I), (II) and(III) is an alkyl group containing from 1 to 6 carbon atoms. Thereaction is a Grignard type reaction and is typically conducted byadding the haloalkoxybenzene/halobenzene mixture to a suspension ofmagnesium in an ether-based solvent at a 1:1 molar ratio. Then thephosphorus oxychloride is added to the formed Grignard reagent at amolar ratio of at least 1:3 (POCl₃:Grignard). The reaction is generallycarried out at a temperature of about 60° C. to about 110° C. for about1 to about 3 hours for each step. In the case of mixture (ii), theoverall reaction can be represented as follows:

By varying the relative amounts of the halobenzene and the mixture ofortho and para-haloalkoxybenzenes reacted with the phosphorusoxychloride, it is possible to control the relative amounts of thefirst, second and third mixtures in the product of the Grignardreaction. In addition, the Grignard product will also normally containtriphenyl phosphine oxide compounds of the formula IV:

in amounts up to 5 or 10 wt % of the product. Although excess amounts oftriphenyl phosphine oxide can be removed by the appropriate workupprocedure, the present composition can contain up to 10 wt % oftriphenyl phosphine oxide without substantial deleterious effect on theutility of the composition in producing epoxy resin compositions.

The mixture of alkoxyphenyl phosphine oxide isomers produced by theGrignard reaction can be converted to a mixture of hydroxyphenylphosphine oxide isomers by reacting the as-synthesized product with anacid, normally hydrogen bromide. This is conveniently effected byrefluxing the alkoxyphenyl phosphine oxide isomers with 48% HBr forseveral hours and not only converts the product to its active hydroxylform but also generates alkyl bromide, in this case methyl bromide, thatcan be recycled to the initial reaction with phenol.

The resultant hydroxyphenyl phosphine oxide composition can be usedeither (a) directly to produce curable, flame retardant epoxy resins or(b) as a crosslinking agent to produce cured, flame retardant epoxyresins.

To produce curable, flame retardant epoxy resins, the presenthydroxyphenyl phosphine oxide composition is conveniently reacted withan epihalohydrin, such as epichlorohydrin, to produce the correspondingglycidyl ether derivatives. These ether derivatives are epoxy resins andcan be cured with standard hardeners such as a combination ofdicyandiamide and 2-methylimidazole. The present phenolic mixtures canalso act as hardeners themselves. Other phenolic hardeners include, butare not limited to, phenolic resins obtained from the reaction ofphenols or alkyl-substituted phenols with formaldehyde, such as phenolnovolaks, cresol novolaks, and resoles. Other hardeners include amines,anhydrides, and combinations involving amines with Lewis acids. Aminehardeners include, but are not limited to, alkyl amines, aryl amines,amides, biguanide derivatives, melamine and guanamine derivatives,methylene-dianiline, diaminodiphenylsulfone, imidazoles,ethylenediamine, diethylenetriamine, polyamides, polyamidoamines,imidazolines, polyetheramines, araliphatic amines, dicyandiamide, andm-phenylenediamine. Combinations of nitrogen-containing catalyst withLewis acids include the heterocyclic secondary and tertiary amines andthe Lewis acids include oxides and hydroxides of zinc, tin, silicon,aluminum, boron, and iron. Other curing agents include carboxylic acidsand anhydrides, amino-formaldehyde resins, and amine-boron complexes.Many types of curing agents that would be useful can be found in anybasic epoxy resin text. In addition, the resins described herein may beformulated with additional additives and fillers to affect cure rate,enhance flame retardancy, and increase the physical properties of thecured epoxy resin composition.

Typically, fillers and reinforcing agents include mica, talc, kaolin,bentonite, wollastonite, glass fiber, glass fabrics glass matt, milledglass fiber, glass beads (solid or hollow), silica, or silicon carbidewhiskers and so forth. Many of these materials are enumerated in theEncyclopedia of Materials Science and Engineering, Vol. #3, pp.1745-1759, MIT Press, Cambridge, Mass. (1986), the disclosure of whichis incorporated herein by reference. Combinations of fillers arepreferred in some embodiments; whereas in other embodiments, thereinforcing agent makes up most of the final composite, as in the caseof glass fabric used in prepregs and laminates for printed wiringboards.

Additionally, the curable epoxy resin described herein may be formulatedwith other flame-retardant materials as co-additives to improve theirperformance. These co-FR materials could be either inorganic or organicand can be reactive or additive based compounds. Examples of inorganicadditive type materials include, but are not limited to, aluminumtrihydrate (ATH), magnesium hydroxide, barium hydroxide, calciumcarbonate, titanium dioxide, and silicon dioxide. Examples of organicbased additives or reactives include, but are not limited to, triphenylphosphate, resorcinol bis(di-2,6-xylyl phosphate),9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), DOPO-basedepoxy resins, bisphenol A bis(diphenyl-phosphate), melamine, melaminephosphate, melamine borate and many others familiar to one skilled inthe art.

Alternatively, the present hydroxyphenyl phosphine oxide composition canbe used as a crosslinking agent for epoxy resins, either alone or incombination with a phenolic co-crosslinking composition. Suitablephenolic co-crosslinking compositions comprise novolac resins, such asphenol-formaldehyde resins, cresol-formaldehyde resins, and mixturesthereof. A polymer of a phenol, nitrogen heteroaryl compound andaldehyde is also suitable. Examples includebenzoguanamine-phenol-formaldehyde resins,acetoguanamine-phenol-formaldehyde resins, melamine-phenol-formaldehyderesins, benzoguanamine-cresol-formaldehyde resins,acetoguanamine-cresol-formaldehyde resins, melamine-cresol-formaldehyderesins, and mixtures thereof.

Representative epoxy resins suitable for use with the presenthydroxyphenyl phosphine oxide composition are presented in Epoxy ResinsChemistry and Technology, Second Edition edited by Clayton A. May(Marcel Dekker, Inc. New York, 1988), Chemistry and Technology of EpoxyResins edited by B. Ellis (Blackie Academic & Professional, Glasgow,1993), Handbook of Epoxy Resins by H. E. Lee and K. Neville (McGrawHill, New York, 1967), and EP 1116774 A2. Suitable epoxy resins are, butnot limited to, epoxy resins based on bisphenols and polyphenols, suchas, bisphenol A, tetramethylbisphenol A, bisphenol F, bisphenol S,tetrakisphenylolethane, resorcinol, 4,4′-biphenyl, dihydroxynaphthylene,and epoxy resins derived from novolacs, such as, phenol:formaldehydenovolac, cresol:formaldehyde novolac, bisphenol A novolac, biphenyl-,toluene-, xylene, or mesitylene-modified phenol:formaldehyde novolac,aminotriazine novolac resins and heterocyclic epoxy resins derived fromp-amino phenol and cyanuric acid. Additionally, aliphatic epoxy resinsderived from 1,4-butanediol, glycerol, and dicyclopentadiene skeletons,are suitable, for example. Many other suitable epoxy resin systems areavailable and would also be recognized as being suitable by one skilledin the art.

It is generally advantageous to use an epoxy resin which possesses onaverage more than 1 and preferably at least 1.8, more preferably atleast 2 epoxy groups per molecule. In the most preferred case the epoxyresin is a novolac epoxy resin with at least 2.5 epoxy groups permolecule. In the broadest aspect of the invention, the epoxy resin maybe any saturated or unsaturated aliphatic, cycloaliphatic, aromatic orheterocyclic compound which possesses more than one 1,2-epoxy group.Examples of heterocyclic epoxy compounds are diglycidylhydantoin ortriglycidyl isocyanurate (TGIC).

EXAMPLES Example 1 Preparation of Anisole

Phenol (150.0 g) was charged into a stirred pressure reactor and thereactor was purged with nitrogen and sealed. Sodium hydroxide (50%,127.7 g) was pumped into the reactor with 163.3 g additional water. Thesolution was agitated for 30 minutes to form the sodium phenolate saltat room temperature after which time methyl bromide (182.0 g) wascharged by vacuum over 1 hour at <−20° C. The reactor was then heated to95-100° C. and held for 4 h to complete the reaction. The reactor wascooled to room temperature then purged with nitrogen to remove anyexcess methyl bromide. The crude organic phase had the followinganalysis by GC: 5.2% phenol, 94.2% anisole.

Example 2 Preparation of Bromoanisole Isomeric Mixture

A 250 mL, round-bottom, 4-neck flask equipped with a mechanical stirrer,a thermocouple, a condenser, and a Teflon feed line connected to asyringe pump was charged with half of the reaction mixture from theabove anisole preparation. Concentrated HCl (97.2 g) was added and themixture was stirred at 30-35° C. Hydrogen peroxide (77.6 g, 35%solution) was metered in over 1.5 hours while the temperature wasmaintained. The contents of the flask were stirred for an additional 2 hto complete the reaction. The reaction was quenched with a 5% Na₂S₂O₅solution and phase separated prior to analysis. The crude organic oillayer had the following analysis by GC: 29.5% anisole, 61.3%4-bromoanisole, 2.5% 2-bromoanisole, 2.6% 2,4-dibromoanisole, 4.1% unkn.This equates to 96.1% selectivity for 4-bromoanisole vs. dibromoanisole.The unreacted anisole can be recovered for re-use and the heavydibromoanisole can be separated from the monobromoanisoles bydistillation. The ratio of 4-bromoanisole (4-BA) to 2-bromoanisole(2-BA) was 96:4. Several runs in this fashion gave a ratio of 4-BA to2-BA ranging from 94:6 to 97:3.

Example 3 Preparation of Mixed Methoxyphenyl Phenyl Phosphine Oxideswith 97:3 4-BA:2-BA Ratio

A flame dried 5 L 4-neck round bottom flask equipped with a mechanicalstirrer, thermocouple, syltherm condenser, heating mantle, additionfunnel and nitrogen purge was charged with magnesium pieces (146.8 g)and 2-methyltetrahydrofuran (MTHF) (1240.3 g) and heated to reflux undernitrogen for 1 h. A 20-g portion of a 692.1-g charge of a 97/3 4-BA/2-BAmixture from above was added carefully making to ensure safe initiationof the reaction, then the remaining mixture was added over time as thereflux could be controlled. When the BA addition was complete, 258.9 gof chlorobenzene was charged all at once and the reaction was held atreflux 6 h to complete the reaction. Next, 306.7 g of POCl₃ was addedunder reflux and the resulting reaction mixture was held at reflux for 2h, after which the reaction mixture was added to dilute HCl and theproduct organic solution phase was separated (2065.9 g). Analysis: 2.24%bromide; 0.57% chloride; 3.9% water; 30.9% solids.

Example 4 Preparation of Mixed Methoxyphenyl Phenyl Phosphine Oxideswith 90:10 4-BA:2BA Ratio

The procedure of Example 3 was repeated using a 90:10 4-BA:2-BA ratio togive 2058.2 g of crude product solution. Analysis: 2.32% bromide; 0.56%chloride; 4% water; 31.3% solids.

Example 5 Preparation of Mixed Hydroxyphenyl Phenyl Phosphine Oxideswith 97:3 4-BA:2BA Ratio

The 2031.9 g of the product solution from Example 3 was stripped toremove solvent. Then 48% HBr (1685.4 g) was charged to the moltenmaterial at ˜100-110° C. and the mixture was heated to reflux. Thereaction reflux temperature was maintained at ˜122° C. by slow removalof aqueous distillate as needed. The reaction was held for 20 h. A 20%ethanolamine scrubber was used to remove the methyl bromide off gas. Thereaction was then cooled to 100° C., washed with water, re-dissolved inMTHF at neutral pH and washed again with water to remove ionicimpurities. The solution was then dried and the product was isolated byevaporating the solvent to give a solid product (484.8 g). Analysis: 171hydroxyl equivalent weight.

Example 6 Preparation of Mixed Hydroxyphenyl Phenyl Phosphine Oxideswith 90:10 4-BA:2BA Ratio

The procedure of Example 5 was repeated using the product of Example 4as starting material. The final product was obtained in 454 g yield.Analysis: 179 hydroxyl equivalent weight.

Example 7 Preparation of Mixed Hydroxyphenyl Phenyl Phosphine Oxideswith 80:20 4-BA:2BA Ratio

The procedures of Example 3 and 5 were repeated using a 80:20 4-BA:2-BAratio as starting material.

Example 8 Preparation of Epoxy Resin of Mixed Hydroxyphenyl PhenylPhosphine Oxides Using Epichlorohydrin

A mixed hydroxyphenyl phenyl phosphine oxide mixture (961.0 g, 3.10mol), epichlorohydrin (2052.0 g, 22.18 mol), and methyl cellosolve (100g) are heated to 80° C. and solid sodium hydroxide (260.4 g, 6.51) isadded slowly over 1.5 h. The reaction vessel is cooled during additionif necessary by an ice-bath to control exotherm. The volatiles areremoved under vacuum, methylene chloride (3 L) is added and theresulting mixture is filtered to remove sodium chloride. The organicsare concentrated under vacuum and Dowanol PM solvent (258 g) is added togive a resin solution.

Example 9 Preparation of Curable Resin Varnish Using Epoxy Resin ofMixed Hydroxyphenyl Phenyl Phosphine Oxides

The glycidyl phosphine oxide from example 8 is mixed with (200 g, 0.947equiv), DEN 438 (100 g, 0.562 equiv), and SD 1708 (158.5 g, 1.51 equiv)using Dowanol PM as solvent to form a curable resin varnish,

Example 10 Laminate Formulation Based on Mixed Hydroxyphenyl PhenylPhosphine Oxides as Co-Curing Agent

A sample of a phosphine oxide mixture from Example 5 was mixed with thephenolic novolac resin SD-1708 and dissolved in Dowanol PM. Thissolution was added to DEN 438 epoxy resin and ATH to form a varnish.Additional solvent was added to achieve the desired resin viscosity. Thevarnish was coated onto eight plies of 7628 glass fabric, B-staged at170° C., stacked with copper foil, and pressed at 170° C., to give alaminate board. This procedure was repeated for the products of examples6 and 7 and product produced according to U.S. Pat. No. 6,733,698 togive the systems depicted in the following table.

Laminate Results Using Mixed Hydroxyphenyl Phenyl Phosphine Oxides(HPPPO) Made from Different Bromoanisole Isomer Ratios.

Formulation No. 1 2 3 4 4-BA/2-BA Ratio 100:0 97:3 90:10 80:20 (U.S.Pat. No. 6,733,698) Formulation, phr DEN 438 100 100 100 100 HPPPO 5556.6 57.4 61.6 SD-1708 25 21.6 28.4 28.1 ATH 54 54.5 55.5 56.7 2-MI 0.06— — — Laminate Properties Tg, ° C. (DSC) 166 — 123 124 Tg, ° C. (TMA)146 156 139/152 pc 128/140 pc TGA 5% 378 391 386 385 T-288, min. N/A >60min >60 >60 UL-94 V-0 V-0 V-0 V-1 pc = laminate post-cured at 220° C.for 4 hr.

As seen in the table above, the laminate made from 97:3 p/o-BA materialdid not display a drop in Tg relative to the 100% para case (as the Tgcould not be seen in the DSC for this laminate formulation, the TMAresults need to be compared). The thermal properties and the burnresults are not compromised when this isomeric mixture was used. Resultsobtained using 90:10 and 80:20 mixtures show that the relevant physicalproperties begin to deteriorate as the amount of o-BA becomes larger.

What is claimed:
 1. An epoxy resin composition comprising the reactionproduct of an epihalohydrin and a hydroxyphenyl or alkoxyphenylphosphine oxide composition comprising: (i) from about 10 to about 50 wt% of a first mixture of mono-(hydroxyphenyl) or (alkoxyphenyl) phosphineoxide isomers each having the formula (I):

(ii) from about 30 to about 60 wt % of a second mixture ofbis-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers eachhaving the formula (II):

(iii) from about 10 to about 50 wt % of a third mixture oftris-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers eachhaving the formula (III):

iv) 0 to 10 mol % of triphenyl phosphine oxides of the formula IV:

wherein R is hydrogen or an alkyl group containing from 1 to 6 carbonatoms, R¹ and R² are the same or different and each is an alkyl groupcontaining from 1 to 6 carbon atoms, each of x and y is an integer from0 through 4, and each OR group is in the ortho or para position withrespect to the bond between the P atom and the associated phenyl groupsuch that, for each mixture (i), (ii) and (iii), the ratio of the numberof OR groups in the ortho-position with respect to the bond between theP atom and the associated phenyl group to the number of OR groups in thepara-position with respect to the bond between the P atom and theassociated phenyl group is from about 20:80 to about 3:97.
 2. The epoxyresin composition of claim 1, wherein each of x and y is zero.
 3. Theepoxy resin composition of claim 1, wherein R is hydrogen.
 4. The epoxyresin composition of claim 1 comprising about 15 to about 30 wt % of thefirst mixture (i), about 40 to about 55 wt % of the second mixture (ii)and about 15 to about 30 wt % of the third mixture (iii).
 5. The epoxyresin composition of claim 3 comprising from 1 to 10 wt % of triphenylphosphine oxides of the formula IV:


6. A curable epoxy resin composition comprising (a) an epoxy resin and(b) a cross-linking system comprising a hydroxyphenyl or alkoxyphenylphosphine oxide composition comprising: (i) from about 10 to about 50 wt% of a first mixture of mono-(hydroxyphenyl) or (alkoxyphenyl) phosphineoxide isomers each having the formula (I):

(ii) from about 30 to about 60 wt % of a second mixture ofbis-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers eachhaving the formula (II):

(iii) from about 10 to about 50 wt % of a third mixture oftris-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers eachhaving the formula (III):

iv) 0 to 10 mol % of triphenyl phosphine oxides of the formula IV:

wherein R is hydrogen or an alkyl group containing from 1 to 6 carbonatoms, R¹ and R² are the same or different and each is an alkyl groupcontaining from 1 to 6 carbon atoms, each of x and y is an integer from0 through 4, and each OR group is in the ortho or para position withrespect to the bond between the P atom and the associated phenyl groupsuch that, for each mixture (i), (ii) and (iii), the ratio of the numberof OR groups in the ortho-position with respect to the bond between theP atom and the associated phenyl group to the number of OR groups in thepara-position with respect to the bond between the P atom and theassociated phenyl group is from about 20:80 to about 3:97.
 7. Thecurable epoxy resin composition of claim 6, wherein each of x and y iszero.
 8. The curable epoxy resin composition of claim 6, wherein R ishydrogen.
 9. The curable epoxy resin composition of claim 6 comprisingabout 15 to about 30 wt % of the first mixture (i), about 40 to about 55wt % of the second mixture (ii) and about 15 to about 30 wt % of thethird mixture (iii).
 10. The curable epoxy resin composition of claim 8comprising from 1 to 10 wt % of triphenyl phosphine oxides of theformula IV: